A ±0.15 %RH Inaccuracy Humidity Sensing System with ±0.44 °C (3σ) Inaccuracy On-Chip Temperature Sensor

This article describes a high accurate humidity sensing system. The humidity sensor and the interface circuit of our system-in-package (SiP) are 3-D stacked to optimize integration density with small foot print. A single reconfigurable ADC is utilized for both 3-D stacked humidity and on-chip temperature sensors. An incremental $\Delta \Sigma $ ADC with a reconfigurable $\Delta \Sigma $ modulator is employed with dual input stages. With the combination of chopping, correlated double sampling (CDS), dynamic element matching (DEM), and system-level chopping techniques, high accuracy sensing system is achieved. The interface circuit, implemented in a standard CMOS $0.18~\mu \text{m}$ CMOS technology, occupies an area of 1.24 mm $^{\mathbf {2}}$ . The SiP sensing system dissipates only $146.5~\mu \text{A}$ and $25~\mu $ A from 3.3 V supply and 1.8 V supply, respectively. Its humidity inaccuracy is 0.15 %RH with a resolution of 0.012 %RH, while a temperature inaccuracy is 0.44 °C ( $3\sigma $ ) with a resolution of 0.015 °C.